cnat n f x = iterate f x !! n
           = (!!n) (iterate f x)
           = (!!n) ((iterate f) x)
           = ((!!n).(iterate f)) x
           = (((!!n).) (iterate f)) x
           = ((((!!n).).iterate) f) x
           = (((!!n).).iterate) f x

cnat n = ((!!n).).iterate